1. Field of the Invention
The invention relates to materials derived from traditional Chinese herbs and to pharmaceutical compositions containing them which are useful in the treatment of atopic disease, in particular atopic eczema, and in treatment of other skin disorders such as non-atopic eczema and psoriasis.
2. Background Information
It is to be understood that by the term Chinese herb is meant any herb which is used by traditional medicine practitioners, usually, but not exclusively, Chinese.
Practitioners of traditional Chinese medicine treat diseases using a system of anatomy and diagnosis totally different from that used in the west. The remedies prescribed are usually a plurality of Chinese herbs which are prepared for administration by the traditional method of decoction i.e. boiling the herbs in water. The herbs are removed and the water maintained for oral, parenteral or topical administration to the patient as appropriate.
Prescriptions for use in this kind of therapy may call for the use of ten or more herbs in combination and traditional Chinese medicine teaches that all of the herbs are necessary to achieve a balanced prescription. A prescription is seen as a balanced whole containing the hierarchy of herbs to which are attributed different functions in treating different manifestations and symptoms of disease.
The identification of herbs which have acceptable clinical activity for any particular human disease while, at the same time having low toxicity, has been made by observation and trial and error over very many years. In some cases prescriptions of traditional Chinese herbs can effectively treat diseases which are not well served by Western monotherapy.
Diseases which appear to respond to the use of a plurality of Chinese herbs are those where there is obscure and complex causality. A particular example is atopic eczema, in which there is chronic inflammation of the skin which is initiated and maintained by a number of different mediators, only some of which are known. Some are related to antigen-antibody reactions. Many others are suspected but not yet defined. Single therapeutic agents like non-steroidal anti-inflammatory drugs which interact with specific inflammatory mediators such as prostaglandins are ineffective in severe atopic eczema. On the other hand corticosteroids have multiple pharmacodynamic actions and are effective in eczema. It appears therefore that the treatment of severe atopic eczema requires a simultaneous attack on a number of pathological lesions, probably related to the immune process in cells and body fluids. While corticosteroids and some immune suppressants have the required broad spectrum of activity for such an attack, their use is limited because of their toxicity. Traditional Chinese herbal remedies known for the treatment of eczema would seem to possess the necessary activity of corticosteroids and immune suppressants but not their toxicity.
A prescription of the Chinese herbs with one selected from each of the following herbs and their Pin yin equivalents or designated by their Materia Medica names: Radix Ledebouriella, Fructus Tribuli, Herba Potentilla chinensis, Caulis Clematis armandii, Radix Rehmannia, Radix Glycyrrhiza, Radix Paeonia rubra, Cortex Dictamni radicis, Herba Lopatheri and Spika Schizonepetae has been used to effectively treat atopic eczema and psoriasis. The clinical efficacy of such a prescription in children with atopic eczema is described by Sheehan et al in British Journal of Dermatology (1992) 126 pp 179-184 and in adults, again by Sheehan et al, in The Lancet (1992) July 4th pp 13-17. A particular method for preparing an extract of those same 10 herbs for use in treating atopic eczema and other inflammatory diseases of the skin is described in GB-A-2254783.
While a decoction of the above-described 10 herbs is known to be effective, the use of a complex prescription containing a plurality of herbs is expensive and it is therefore desirable to simplify the prescription if this can be done without compromising activity and/or safety. It would also be preferable to limit any prescription to herbs which might be grown in the UK or Europe rather than relying on import from China. Thus many attempts have been made to identify the active principle or principles in prescriptions of traditional Chinese medicines. In the case of eczema however this has proved difficult because hitherto there has been no validated animal or in vitro model for the disease which could be used to identify clinical activity in fractions or pure substances prepared from the crude herbs.
Now however an in vitro assay has been developed which appears to be predictive of clinical efficacy in atopic eczema and other atopic diseases and this has allowed the present inventors to detect active components in freeze-dried decoctions (hereinafter referred to as PSE222) of the 10 herbs listed above.
Although traditional Chinese wisdom dictates that a plurality of herbs is required, the use of this in vitro method and confirmation by in vivo clinical experiments has shown that the desired clinical effect can be reproduced by a subset of the 10 herbs and by individual components within them. Furthermore, the method has also permitted identification of components in PSE222 which may initiate worsening of the atopic condition and which it is desirable to remove from any extract for pharmaceutical use.
The in vitro test for efficacy is based on the observation that in atopic disease and in particular atopic eczema, skin cells and monocytes from human peripheral blood express a cell surface marker antigen CD23 and that the expression of CD23 is inhibited or reduced on successful treatment of the eczema. (see Takigawa et al, Clin. Exp. Immunol. (1991) 84 pp 275-282). CD23 expression can also be induced in vitro in human monocytes by exposure to the cytokine interleukin 4 (IL4) and in parallel with the in vivo situation described by Takigawa above the induction is inhibited by compounds known to be useful in atopic disease. These observations therefore provide the basis for a simple in vitro assay in which monocytes prepared from human peripheral blood are brought into contact simultaneously with IL4 and the active agent to be tested. The amount of CD23 expression is measured using labelled monoclonal antibodies to CD23 and any effect expressed as a percentage inhibition of CD23 expression compared to a control in which saline or a placebo preparation of herbs replaces the test material. That significant inhibition of CD23 expression in this in vitro test is predictive of clinical efficacy is demonstrated by the fact that the extract PSE222, prepared from the 10 herbs listed above which have been successfully used clinically for atopic eczema, shows an inhibition of CD23 expression in the assay of 50 to 60%.
Using the above assay the present inventors have identified components in PSE222 suitable for clinical use in atopic disease generally and also in the treatment of particular skin diseases such as non-atopic eczema and psoriasis.
Thus in accordance with a first aspect of the invention there is provided a material suitable for the treatment of atopic disease, non-atopic eczema or psoriasis which can be extracted from a freeze-dried decoction of a mixture comprising the following Chinese herbs:
Radix Ledebouriella
Fructus Tribuli
Herba Potentilla chinensis
Caulis Clematis armandii
Radix Rehmannia
Radix Glycyrrhiza
Radix Paeonia rubra
Cortex Dictamni radicis
Herba Lopatheri
Spika Schizonepetae
said material comprising one or more of those components present in the freeze-dried decoction which run with Rf values in the ranges 0.00 to 0.100, 0.167 to 0.300, 0.400 to 0.533, 0.700 to 0.833 or 0.900 to 0.967 if said freeze-dried decoction is diluted in aqueous solution and subjected to chromatography on a Whatman 2 cmsxc3x9755 cms 3MM cellulose strip for 10 hours using a solvent mixture of butanol, ethanol and water in the proportions 4:1:1.
Preferably said material comprises one or more of those components present in the freeze-dried decoction which run with Rf values in the range 0.00 to 0.100.
When the cellulose strip is subjected to a water extraction after the solvent front has run some 30 cm or so those components extracted with the water having Rf values roughly in the ranges given above cause significant reduction of CD23 antigen on human monocytes treated in vitro with IL4. If the cellulose strip is subsequently extracted with methanol, the methanol extracts for those components having an Rf values roughly in the ranges 0.700 to 0.833 or 0.900 to 0.967 also cause significant reduction in CD23 expression in vitro.
Furthermore, and surprisingly, following a water extraction and subsequent methanol extraction of the cellulose strip, those methanol extracts of components running with Rf values in the ranges of 0.067 to 0.333 and 0.533 to 0.700 when tested in the CD23 assay, enhance or increase the expression of the CD23 antigen compared to controls. The presence of the xe2x80x9cenhancerxe2x80x9d activity in any preparation for the treatment of atopic or non-atopic eczema or other atopic disease is clearly undesirable and enhanced clinical activity is thus predicted on its removal. A significant amount of the xe2x80x9cenhancerxe2x80x9d activity may be removed by extraction of PSE222 or other preparation of the 10 herbs listed above with a non-polar solvent such as hexane.
Therefore in accordance with a second aspect of the invention there is provided a material for the treatment of atopic eczema, non-atopic eczema or psoriasis which comprises a decoction or extract of a mixture including the ten Chinese herbs listed above which has had those components, extractable with hexane or other non-polar solvent, removed. A decoction or extract so treated demonstrates significant inhibition of CD23 expression on human monocytes in the above described in vitro assay which is indicative of its potential clinical efficacy.
Decoctions of the individual herbs from the above list of ten have been tested for their ability to inhibit CD23 expression in vitro and this has lead to the identification of a subset of herbs predicted to have good clinical efficacy.
In accordance with a third aspect of the invention there is provided a material for the treatment of atopic disease, non-atopic eczema or psoriasis which comprises a decoction or extract of one or more of the following sets of Chinese herbs:
(a)
Radix Paeonia rubra
Radix Glycyrrhiza
Radix Rehmannia
(b)
Cortex Dictamni
Radix Paeonia rubra
Radix Glycyrrhiza
Radix Rehmannia
Radix Ledebouriella
Fructus Tribuli or
(c)
Radix Paeonia rubra
Radix Glycyrrhiza
Spika Schizonepetae
in the substantial absence of any other Chinese herbs. Preferably such a decoction or extract is treated so that those components extractable with hexane or other non-polar solvent have been removed. The sets of herbs specified under (a) and (c) above have the advantage that all the herbs used can be grown in Europe.
In accordance with a fourth aspect of the invention there is provided a material for treatment of atopic disease, non-atopic eczema and psoriasis which comprises a decoction or extract from one or more of the herbs Cortex Dictamni, Radix Paeonia rubra, Radix Rehmannia, Radix Glycyrrhiza or Spika Schizonepetae in the substantial absence of any other Chinese herbs. Again, preferably such extracts or decoctions are subject to extraction with a non-polar solvent such as hexane.
Production of the active components of PSE222 on a commercial scale may be achieved by contacting a freeze-dried decoction with fibrous cellulose, of which suitable grades are available commercially, followed by mixing with a suitable solvent such as the butanol/ethanol/water mix as described above or butanol/IMS (Industrial Methylated Spirit)/water mix in the proportions 4:1:1 to remove bulk and inactive materials. Centrifugation of the mix then yields a precipitate which can be reextracted with the above solvent mix several times before drying and mixing with water to extract the active components for formulation as pharmaceutical preparations.
The materials of the first, second, third and fourth aspects of the invention, whether or not produced by the above-described commercial process, are preferably prepared as pharmaceutical compositions by mixing with any suitable pharmaceutical carrier or diluent, of which a great many are known in the art. Compositions suitable for treatment of atopic disease generally, and in particular atopic eczema or for non-atopic eczema or psoriasis may be formulated for oral, topical or parenteral administration. Oral formulations may be prepared in unit dosage forms as for example tablets, powders or granules or may be a liquid preparation for drinking.
It will be appreciated that the in vitro assay described above may be used as an indicator of any compound or preparation which is likely to be clinically active against atopic eczema and dermatitis irrespective of geographical or botanical origin.
Thus in accordance with a fifth aspect of the invention there is provided a method for indicating the clinical activity of a compound or preparation against atopic eczema or dermatitis which comprises the steps of:
(a) incubating peripheral blood monocytes in vitro simultaneously or sequentially with interleukin 4 (IL4) and the compound or preparation whose activity is to be tested,
(b) measuring the expression of the cell surface marker CD23 on said monocytes and
(c) using the measurements obtained in step (b) as an indication of potential clinical efficacy of the compound or preparation against atopic eczema or dermatitis by comparing the level of IL4 induced CD23 expression of the monocytes in the presence or absence of said compound or preparation.
An inhibition of CD23 expression of greater than 25% is statistically significant and indicates a compound or preparation which may be clinically useful.